Formerly there were "dime stores" and now there are "dollar stores". So the currency has been diluted ~~10x over a period of [something less than] a century.

Formerly there were "dime stores" and now there are "dollar stores". So the currency has been diluted ~~10x over a period of [something less than] a century. So every unit is now 0.1 of what it was when the decisions were made that still govern the size, weight, and quantity of production of both coins and paper currency. Today's penny is what used to be a "mill", one-tenth of a cent, a unit still used locally within living memory but issued at the state level rather than by the U. S. Mint. Half-cents were scrapped as long ago as 1857; they would be today's nickel (or more). The Canadians, Australians, Brits, and Europeans have it right: useful coins today would be 10, 20, 50 cents, 1 dollar, and 2 dollars. (I suppose we can grant the quarter legacy status, even though it originated from a crown-size coin that was so thin that it could be bent and broken in half, then in half again.)